| Summary: | Lipoprotein lipase (LPL) is a key enzyme in lipoprotein and energy metabolism and, therefore, regulation of its expression could have an important bearing on these processes. We have identified an evolutionarily conserved 5′-CCTCCCCCC-3′ motif (from −91 to −83, CT element) in the human LPL gene promoter, deletion or mutation of which caused approximately 70–80% decrease in promoter activity. We found that Sp1 and Sp3 in THP-1 nuclear protein extracts bind specifically to this element. Co-transfection with Sp1 and Sp3 expression plasmids transactivated the LPL promoter via the CT element in Drosophila SL2 cells devoid of Sp proteins. Sp3 moderately repressed Sp1-mediated LPL promoter activation when both were co-expressed in SL2 cells. Furthermore, co-expression of an active sterol regulatory element binding protein (SREBP-1), with Sp1, but not with Sp3, synergistically activated the LPL promoter in SL2 cells. We previously reported a naturally occurring T→G substitution at position −93 of the human LPL promoter which reduces promoter activity by 40–50% in transient transfection assays. In this study, we showed that this substitution results in reduced binding affinity to Sp1/Sp3 and in diminished transactivation by Sp1/Sp3 alone and by the synergistic action of Sp1 and SREBP-1. In conclusion, recruitment of Sp1/Sp3 by the CT element may play an important role in expression of the human lipoprotein lipase gene. Synergistic transcriptional activation by Sp1 and SREBP-1 may provide a mechanism for cross-talk between cholesterol and triglyceride metabolic pathways.—Yang, W-S., and S. S. Deeb. Sp1 and Sp3 transactivate the human lipoprotein lipase gene promoter through binding to a CT element: synergy with the sterol regulatory element binding protein and reduced transactivation of a naturally occurring promoter variant. J. Lipid Res. 1998. 39: 2054–2064.
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